1. Field
Example embodiments relate to a semiconductor optoelectronic device having higher optical efficiency and method of fabricating the same.
2. Description of the Related Art
A semiconductor laser device is one kind of a nitride-based compound semiconductor opto-electronic device. Such nitride-based light emitting devices use sapphire as the material for forming the substrate. In general, a wave guide layer is formed of GaN to guide light formed in an active layer of the nitride-based laser diode. A clad layer is formed of AlxGa1-xN to confine light and electrons.
AlxGa1-xN has a larger energy gap than GaN and a larger refractive index difference from InGaN as an active layer than GaN as a waveguide. An AlGaN layer used as a clad layer has a higher lattice parameter and a higher thermal expansion coefficient than a wave guide layer and GaN used as a n-type contact layer. Thus, cracks are formed. As a result, the composition ratio and the thickness of Al of AlxGa1-xN are limited. According to recent research results, a composition ratio of Al of an AlGaN/GaN supper lattice is limited to about 14%, and the thickness of Al is confined to 1 μm. A composition ratio of Al of bulk AlGaN is limited to 8%, and the thickness of Al is confined to 1 μm.
An improvement of the optical confinement effect is limited by the thickness of the clad layer and ratio of Al. In other words, the optical confinement factor (OCF) may be reduced, and the threshold current may be increased. Thus, it is difficult to improve the internal quantum efficiency and optical power of a semiconductor opto-electronic device.